1. Field of the Invention
The present invention relates to a process for preparing allyl acetate from propylene, acetic acid and oxygen in the gas phase.
2. Description of the Related Art
Many reports have been published on catalysts to be used for preparing allyl acetate from propylene, acetic acid and oxygen in the gas phase. Most of these catalysts comprise palladium as the main catalyst and at least one metal selected from the group consisting of alkali metals, alkaline earth metals, gold, copper, molybdenum, cadmium, lead, vanadium, bismuth, chromium, tungsten, manganese and iron as the promoter, and these catalyst components are usually supported on alumina, silica, active carbon, pumice, titanium oxide or the like.
When carrying out a reaction by using these catalysts, it is industrially important that the activity of the catalyst is high, the change of the activity over a long period is small, and the selectivity to allyl acetate is high.
Studies of the promoter and carrier are important for obtaining a catalyst having a high activity, a long life, and a high selectivity, but studies on the catalyst-preparing process are as important as the above-mentioned studies. It is broadly and empirically recognized that, even if the catalyst components and carrier are the same, often the reaction results differ greatly due to differences in the catalyst-preparing process.
Accordingly, various proposals have been made with regard to the promoter component, the carrier and the catalyst-preparing process, for improving the catalyst performances such as the activity, and a uniform support of palladium on the carrier is recommended (see, for example, Japanese Examined Patent Publication No. 44-29046, No. 46-23364, No. 50-5685, No. 52-29294 and No. 55-27046, and Japanese Unexamined Patent Publication No. 48-64014, No. 60-32747 and No. 61-238759).
In each of these conventional catalysts, however, the amount of allyl acetate formed in 1 hour per gram of metallic palladium (hereinafter referred to as "relative activity") does not exceed 70 g, and since palladium metal is very expensive, it is considered that the contact efficiency per unit weight of metallic palladium is too low for conducting the preparation of allyl acetate on an industrial scale.